NaCl: Update revision in DEPS, r12730 -> r12747

NaCl: Update revision in DEPS, r12730 -> r12747

This pulls in the following Native Client changes:

r12731: (jvoung) Turn on tests/callingconv_case_by_case for PNaCl --target=i686-nacl.
r12732: (bradnelson) Dropping remaining python_26 references.
r12734: (mcgrathr) Default to all trybot sets when pynacl/ code is touched
r12735: (kschimpf) Add pnacl-compress driver tool to compress pnacl bitcode files.
r12736: (halyavin) Fix more instances of use-after-free due to incorrect clean up.
r12737: (sbc) Update newlib revision used by toolchain builders.
r12738: (dyen) build_nexe.py can now apply tls_edit
r12739: (dyen) tls_edit only prints out verbose messages in scons
r12740: (mseaborn) Remove irt_ppapi.{c,h}, which have been moved to the Chromium repo
r12741: (jfb) Toolchain build: add sync-only option.
r12742: (noelallen) Add a bootstrap target for bionic LIBC to generate only the static libc components.  This will allow libgcc_s to build, which can then be used to link the dynamic libc.
r12743: (mseaborn) Cleanup: Remove "ppapi" directory from IRT's #include search path
r12744: (noelallen) Roll to get missing files
r12745: (mseaborn) Cleanup: Remove PPAPI directories from include_rules, used by checkdeps
r12746: (dschuff) Run LLVM regression tests for toolchain_build_pnacl build
r12747: (noelallen) Roll Bionic in TOOL_REVISIONS

BUG=none
TEST=browser_tests and nacl_integration